The present invention relates generally to a hermetic scroll-type compressor and, more particularly, to such a compressor including an eccentric drive mechanism for drivingly engaging the orbiting scroll member, wherein the drive mechanism includes a crankpin and roller assembly coupled to the orbiting scroll member.
A typical scroll compressor comprises two mutually facing scroll members, each having an involute wrap, wherein the respective wraps interfit to define a plurality of compression pockets. When one of the scroll members is orbited relative to the other, the pockets travel in a radial direction, e.g., from a radially outer suction port to a radially inner discharge port, to convey and compress a refrigerant fluid.
The orbiting scroll member is drivingly engaged by an eccentric crank mechanism to impart orbiting motion thereto. Generally, the crank mechanism is associated with a rotating crankshaft driven by an electric drive motor. More specifically, in a crank mechanism to which the present invention is applicable, the upper end of the rotating crankshaft includes an eccentric crankpin that is drivingly coupled to the bottom surface of the orbiting scroll member. The orbiting scroll member is prevented from rotating about its own axis by a conventional Oldham ring assembly cooperating between the scroll member and a stationary frame member.
During operation of a scroll-type compressor, the pressure of compressed refrigerant at the interface between the scroll members tends to force the scroll members axially and radially apart, thereby permitting high-to-low pressure leakage between compression pockets that reduces the operating efficiency of the compressor. Consequently, axial and radial compliance of the orbiting scroll member toward the fixed scroll member is required in order to maintain the scroll members in sealing contact with one another. Various methods for achieving such axial and radial compliance have been developed, and are widely used in scroll-type compressors.
In the aforementioned eccentric crank mechanism to which the present invention pertains, a swing-link radial compliance mechanism is incorporated. Specifically, the eccentric crankpin on the crankshaft is received within an axial bore extending through a cylindrical roller at an off-center location thereof, whereby the roller is eccentrically journalled about the eccentric crankpin. The roller and crankpin assembly is then received within a cylindrical well formed on the bottom surface of the orbiting scroll member, whereby upon rotation of the crankshaft the orbiting scroll member is caused to orbit. The roller pivots slightly about the crankpin so that the crank mechanism functions as a radial compliance mechanism to promote sealing engagement between the involute wraps of the scroll members.
In the aforementioned eccentric crank mechanisms, and particularly those incorporating a crankpin and roller swing-link radial compliance mechanism, it is desirable to minimize friction at the interfaces between the crankpin, roller, and orbiting scroll member bearing surfaces in order to reduce power losses in the compressor and to prevent overheating and failure of the bearings.
Presently, the bearing surfaces of the crankpin, roller, and orbiting scroll member are lubricated with oil from the oil sump of the hermetic compressor by splashing the oil onto the top axial end of the interfaces between the members. Consequently, oil flows by gravity into the respective interfaces. In the aforementioned crank mechanism wherein the crankpin and roller assembly are received within a well in the bottom surface of the orbiting scroll member, an axial oil passageway extends through the crankpin and has an opening on the axial end of the crankpin adjacent the bottom surface of the well. Oil is delivered into the well and then flows into the previously described interfaces, aided in some instances by flats on the bearing surfaces.
Several problems are possible in the aforementioned lubrication system relating to an eccentric drive mechanism incorporating a swing-link radial compliance mechanism. For instance, oil supplied to the axial end of the bearing surface interfaces may be otherwise vented away without entering the interface. Also, oil entering an axial end of the bearing interfaces may not travel the full axial distance, or may increase in temperature over the axial distance, thereby affecting the quality of lubrication over the axial distance of the bearing interface.